User equipment (UE), also known as mobile stations, wireless terminals and/or mobile terminals are enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The communication may be made e.g. between two user equipment units, between a user equipment and a regular telephone and/or between a user equipment and a server via a Radio Access Network (RAN) and possibly one or more core networks.
The user equipment units may further be referred to as mobile telephones, cellular telephones, laptops with wireless capability. The user equipment units in the present context may be portable and enabled to communicate voice and/or data, via the radio access network, with another entity, such as a network node, for example.
The wireless communication system covers a geographical area which is divided into cell areas, with each cell area being served by a network node, or base station as it also may be referred to, such as e.g. a Radio Base Station (RBS), which in some networks may be referred to as “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and terminology used. The network nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the network node/base station at a base station site. One network node, situated on the base station site, may serve one or several cells. The network nodes communicate over the air interface operating on radio frequencies with the user equipment units within range of the respective network node.
In some radio access networks, several network nodes may be connected, e.g. by landlines or microwave, to a Radio Network Controller (RNC) e.g. in Universal Mobile Telecommunications System (UMTS). The RNC, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural network nodes connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units.
The 3rd Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example by developing Long Term Evolution (LTE) and the Evolved Universal Terrestrial Radio Access Network (E-UTRAN).
LTE is a technology for realizing high-speed packet-based communication that may reach high data rates both in the downlink and in the uplink. In LTE, network nodes, which may be referred to as evolved-NodeBs, eNodeBs or even eNBs, may be connected to a gateway e.g. a radio access gateway, which in turn may be connected to one or more core networks.
In the present context, the expressions downlink, downstream link or forward link may be used for the transmission path from the network node to the user equipment. The expression uplink, upstream link or reverse link may be used for the transmission path in the opposite direction i.e. from the user equipment to the network node.
The network node which is serving a cell, is also determining which user equipment to serve via the network node and which user equipment to reject service when an establishment request is made for a radio access bearer. This is referred to as Admission Control. In mobile radio communication systems, these establishment requests are made for new radio access bearers. The task of the Admission Control is thus to admit or reject resource requests, based on various factors. Admission Control considers the overall resource situation, e.g. in the network nodes and infrastructure comprising both radio access network and core network, the QoS requirements of the radio access bearer, the priority levels and the provided QoS of in-progress sessions and the QoS requirement of the new radio access bearer request. A request for a radio access bearer, for which the requested QoS cannot be met, may consequently be rejected by the network node.
The Scheduler is a functionality within the network node, responsible for dynamically assigning resources to a radio access bearer, such that (i) its requested Quality of Service in terms of for instance delay requirements are met and (ii) its priority level compared to other bearers with Quality of Service requirements are considered. Within the context of this disclosure, the non-limiting examples are given within an E-UTRA context, comprising E-UTRA Radio Access Bearers (E-RABs).
Each request for a radio access bearer, or E-RAB (the expressions may be used interchangeably within the present context), comes with a QoS requirement and a priority number. The Scheduler, upon receiving the request, tries to assign resources to the QoS E-RABs to fulfil their QoS requirements. Whenever the Scheduler is congested, it assigns resources such that the QoS requirements are fulfilled in the order indicated by the priority of the QoS E-RABs.
Scheduling may also consider channel quality. Then E-RABs with good channel quality are selected for scheduling prior to E-RABs with bad channel quality.
It is reasonable to monitor how well the Scheduler succeeds to serve the QoS requirements of the E-RABs. There may be congestion or out-of-coverage scenarios when it is no longer possible to maintain the requested QoS of the E-RAB, no matter what policies are used for scheduling the E-RAB. Whenever the QoS requirement for an E-RAB consistently fails, one may release the QoS E-RAB since it does not anyway contribute to the system capacity.
Since the Scheduler considers a priority whenever the E-RABs are congested, QoS requirements of E-RABs with less important priority tend to get stressed first. This tendency is then followed when releasing E-RABs due to failed QoS. QoS E-RABs are pre-empted, or released, in order of the priority considered by the Scheduler.
A problem that arises is that a pre-empted QoS E-RAB of a certain QoS Class Identifier (QCI) makes its user equipment immediately request for setting up another E-RAB of the same QCI. For example, interrupted voice calls usually results in a redial. Similar kind of behaviour is expected from machine-to-machine applications e.g. in smart phones and tablets.
The QoS prospects for such immediately triggered E-RAB requests are not good since a similar kind of radio bearer with same QCI has been recently dropped due to lack of resources and it may be expected that the situation will not change rapidly.
Thus there are room for improvement of the Admission Control within a network node, in order to better utilise the scheduled resources.